WO2021193144A1

WO2021193144A1 - Method for producing bonding composition

Info

Publication number: WO2021193144A1
Application number: PCT/JP2021/010064
Authority: WO
Inventors: 圭穴井; 真一山内; 亭來趙
Original assignee: 三井金属鉱業株式会社
Priority date: 2020-03-27
Filing date: 2021-03-12
Publication date: 2021-09-30
Also published as: EP4129529A1; EP4129529A4; US20230137716A1; CN115297978A; JPWO2021193144A1; TW202143250A; KR20220154679A

Abstract

The present invention is a method for producing a bonding composition comprising copper particles and a second solvent. In the production method, a dispersion of copper particles is prepared by producing the copper particles in a first solvent by a wet reduction method. Then, while maintaining a wet state for the dispersion, the first solvent in the dispersion is replaced ultimately with a second solvent. Replacing the first solvent with another solvent at least once and using the second solvent for the final replacement is also preferred. Carrying out solvent replacement at below 100°C is also preferred. The use as the second solvent of at least one selected from water, alcohols, ketones, esters, ethers, and hydrocarbons is also preferred.

Description

Method for producing bonding composition

The present invention relates to a method for producing a bonding composition.

With the miniaturization and higher performance of electronic devices, various performance improvements such as dimensional stability, conductivity, and adhesion to members are required in the formation of electronic circuits in electronic devices. In order to realize these requirements, for example, a conductive paste containing a metal powder having less agglutination between particles is desired.

Patent Document 1 includes a step of precipitating a metal powder by a wet reduction method and a step of adding a water-soluble organic solvent to the metal powder in a state where water is attached and replacing the water with the water-soluble organic solvent. A method for producing a conductive paste is disclosed.
Patent Document 2 discloses a method for producing a metal powder for a conductive paste, in which the metal powder is washed with water or an organic solvent together with crushing.
It is also disclosed in each of the above-mentioned patent documents that the dispersibility of the metal powder can be improved.

Further, Patent Document 3 discloses a method for producing a silver-containing powder in which a dispersion liquid of silver-containing particles and a surfactant is vacuum freeze-dried.
Further, Patent Document 4 discloses a silver powder obtained by converting silver particles obtained by a wet reduction method into a wet cake having a predetermined water content and crushing the wet cake by adding a dispersant. ..
Similar to Patent Documents 1 and 2, these patent documents also disclose that the dispersibility of the metal powder can be improved.

Japanese Unexamined Patent Publication No. 2003-151381 Japanese Unexamined Patent Publication No. 2003-253301 US2009 / 146117A1 Japanese Unexamined Patent Publication No. 2007-224422

All of the techniques described in Patent Documents 1 to 4 have investigated the dispersibility of metal particles, but when the obtained metal powder or a conductive paste containing the metal powder is used for sintering, No studies have been made on the adhesion to other members.

The present invention is to provide a method for producing a bonding composition having excellent adhesion to other members at the time of sintering.

In the present invention, copper particles are generated in the first liquid medium by a wet reduction method to prepare a dispersion of the copper particles, and then, after that,
While maintaining the wet state of the dispersion, the first liquid medium of the dispersion is finally replaced with the second liquid medium to obtain a bonding composition containing the copper particles and the second liquid medium. It provides a method for producing a bonding composition.

1 (a) and 1 (b) are ultrasonic images of a sintered body obtained by firing the bonding compositions of Examples and Comparative Examples together with an object to be bonded.

Hereinafter, the present invention will be described based on its preferred embodiment. The method of the present invention relates to the production of a bonding composition containing copper particles and a second liquid medium. The bonding composition is suitably used, for example, as a conductive paste or a conductive ink for bonding two objects to be bonded to each other. In this case, the bonding composition is preferably a dispersion containing copper particles as a conductive filler and a second liquid medium.

The production method of the present invention includes a step of producing copper particles in the first liquid medium by a wet reduction method to prepare a dispersion of copper particles, and a first step of the dispersion while maintaining a wet state of the dispersion. It is roughly divided into two steps, the step of finally replacing the liquid medium with the second liquid medium.
The "wet state" as used herein means a state in which the copper particles are not dried by, for example, heat treatment, and the surface of the copper particles is wet so that the vapor phase and the copper particles do not come into direct contact with each other. Specifically, it refers to a state in which the solid content concentration of the liquid medium dispersion of copper particles is maintained at 95% by mass or less.

Further, "finally replacing the first liquid medium with the second liquid medium" means that the first liquid medium is directly replaced with the second liquid medium, and the dispersion containing the second liquid medium, which is the final object, is contained. And, the first liquid medium is replaced with one or more other liquid media (excluding the first liquid medium and the second liquid medium) other than the second liquid medium, and the final liquid medium replacement In both aspects, in the step, another liquid medium (excluding the first liquid medium and the second liquid medium) is replaced with the second liquid medium to obtain a dispersion containing the second liquid medium which is the final target product. Including.

First, copper particles are generated in the liquid medium by the wet reduction method. The wet reduction method is intended, for example, by mixing a copper compound as a copper source and a reducing compound in a first liquid medium to prepare a reaction solution, and reducing the copper compound in the reaction solution. Obtain copper particles. By producing the copper particles by the wet reduction method, the particle size of the particles can be easily controlled, and spherical particles can be easily obtained. Copper particles can also be produced, for example, by the method described in Japanese Patent Application Laid-Open No. 2015-168878.

In preparing the reaction solution containing the copper compound and the reducing compound, there are no particular restrictions on the order and method of adding the copper compound and the reducing compound. For example, a solid copper compound and a solid reducing compound may be added at the same time to prepare a reaction solution. Further, at least one of the copper compound and the reducing compound may be dispersed or dissolved in the liquid medium in advance, and then one may be added to the other to prepare a reaction solution. When one of the copper compound and the reducing compound is added to the other, it may be added all at once, or may be added continuously or intermittently by a method such as dropping.

As the copper compound, it is preferable to use a compound that dissolves in a liquid medium. Examples of such a copper compound include water-soluble copper (II) salts such as copper chloride, copper acetate and copper sulfate. These copper compounds may be anhydrous or hydrated. These copper compounds can be used alone or in combination of two or more.

The copper compound is preferably 0.001 mol / L or more and 1 mol / L or less, and more preferably 0.1 mol / L or more and 0.5 mol / L or less in terms of the content of the copper element in the reaction solution. Mix. By setting the content of such a copper compound, copper particles having a small particle size can be obtained with high productivity.

The reducing compound reduces the copper ions of the copper source. Examples of the reducing compound include hydrazine compounds such as hydrazine, hydrazine hydrochloride, hydrazine sulfate and hydrous hydrazine, sodium hydride, sodium sulfite, sodium hydrogen sulfite, sodium thiosulfate, sodium nitrite, sodium hyponitrite, and the like. Examples thereof include phosphite, sodium phosphite, hypophosphite, and sodium hypophosphite. These reducing compounds may be anhydrous or hydrated. These reducing compounds may be used alone or in combination of two or more.
In particular, hydrazine is particularly preferably used because it causes less impurities to be generated after reduction and less impurities are mixed into the obtained copper particles. From the viewpoint of strong reducing power and suppressing contamination of particles with impurities, it is more preferable to use only hydrazine anhydride or hydrate as the reducing compound.

The content of the reducing compound in the reaction solution is preferably 0.5 mol or more and 50 mol or less, more preferably 1 mol or more and 10 mol or less, and further preferably 2 mol or more and 5 mol or less with respect to 1 mol of the copper element. By setting the content of the reducing compound to such a ratio, copper particles having a small particle size can be easily obtained. The reduction of the copper compound by the reducing compound may be carried out only once, or may be carried out a plurality of times as necessary. The content of the reducing compound described above is a value in terms of anhydride.

The reaction conditions of the reaction solution may be the reaction without heating from the start of mixing to the end of the reaction, or the reaction may be carried out under heating conditions.
Further, from the viewpoint of uniformly generating the reduction reaction and obtaining copper particles having little variation in particle size, it is also preferable to continue stirring the reaction solution for the entire time from the start of mixing to the end of the reaction.

From the viewpoint of achieving both the progress of the reduction reaction sufficient for the formation of copper particles and the reduction of the production cost, it is preferable to carry out the reaction so as to maintain 0 ° C. or higher and 80 ° C. or lower from the start time of mixing to the end time of the reaction. The time from the start of mixing to the end of the reaction can be appropriately changed depending on the particle size of the target copper particles, but is preferably 0.5 hours or more and 4 hours or less, and more preferably 1 hour or more and 3 hours or less. be able to. When the reduction treatment of the copper compound with the reducing compound is performed a plurality of times, the above-mentioned time is the total of the time from the start time of each mixing to the end time of the reaction.

Copper particles are generated through the above steps. Since the copper particles are obtained by the wet reduction method, they are in the state of a dispersion of copper particles dispersed in the first liquid medium which is the liquid medium of the reaction liquid.

The generated copper particles are preferably 100 nm or more and 300 nm or less, more preferably 100 nm, represented by the _{volume cumulative particle size DSEM50} at a cumulative volume of 50% by volume measured by image analysis of scanning electron microscope observation. It is 250 nm or more and 250 nm or less. Since D _SEM50 indicates the particle size of the primary particle, which is an object recognized as the smallest unit as a particle, judging from the geometrical shape on the outer shape, the copper particle is defined as such a particle size range. As a result, the bonding composition exhibits good packing properties and sinterability, is capable of exhibiting high adhesion to other members such as the object to be bonded, and is advantageous in forming a thin coating film. .. The particle size of the copper particles can be appropriately adjusted, for example, by adjusting the molar ratio of the copper compound and the reducing compound, or by adjusting the time of the reduction reaction.

D _SEM50 can be measured by, for example, the following method. First, using Mac-View, a software manufactured by Mountech, the image data of copper particles obtained by observing from directly above with a scanning electron microscope was read, and then 50 or more copper particles on the data were randomly selected. Then, the particle size (Haywood diameter) of the particles is measured. Next, from the obtained Haywood diameter, the volume when the particles are assumed to be true spheres is calculated, and the volume cumulative particle diameter at 50% by volume of the cumulative volume of the volume is _{defined as DSEM50} .

Subsequently, the first liquid medium of the dispersion is replaced with the second liquid medium while maintaining the wet state of the copper particle dispersion. In this step, in obtaining the desired bonding composition, the first liquid medium in the dispersion is finally contained in the bonding composition while maintaining the wet state of the dispersion. One of the features is to replace it with a second liquid medium.

In the preparation of a bonding composition such as a conductive paste containing copper particles or a conductive ink as a conductive filler, dried copper powder obtained by drying the obtained copper particles is typically used. In this method, the content of copper particles can be appropriately increased or decreased to easily prepare a paste or ink having a desired filler concentration. However, when a bonding composition is prepared using dried copper powder, the redispersion process becomes complicated because the copper particles in the dried copper powder are agglomerated or easily agglomerated. In some cases, redispersion itself became impossible. As a result, the coating film obtained by applying the bonding composition is difficult to be smooth and has poor adhesion to other members. In addition, the surface of the copper particles may be altered by oxidation or the like during drying, and desired properties such as adhesion and conductivity may not be exhibited.
In particular, when copper particles having a particle size suitable for ink or paste are used in a dry state, the complexity of redispersion and the deterioration of the particles due to oxidation and the like are remarkable.

As a result of investigation by the present inventor in order to solve this problem, the copper particles obtained are not dried and are subjected to the subsequent steps while being maintained in a wet state, so that the copper particles come into contact with oxygen in the atmosphere. It will be reduced. Further, by increasing the dispersibility of the copper particles when preparing the bonding composition, excessive stress generation during film formation and sintering is suppressed. As a result, it has been found that the bonding composition of the present invention can exhibit excellent adhesion to other members during sintering and can suppress peeling from other members due to excessive volume shrinkage during sintering. rice field.

Substitution of the first liquid medium to the second liquid medium may be performed directly (hereinafter, this is also referred to as "direct replacement"), and the first liquid medium to another liquid medium (however, the second liquid medium is excluded). ) May be replaced one or more times, and then finally replaced with a second liquid medium (hereinafter, this is also referred to as "indirect replacement"). The dispersions maintained in a wet state can be independently, for example, in the form of a slurry or a wet cake.

The method for replacing the liquid medium is not particularly limited as long as the wet state of the dispersion can be maintained regardless of direct substitution or indirect substitution. For example, repulp washing, decantation method, rotary filter method, filtration and the like are adopted. be able to. Further, the liquid medium may be replaced only once, or may be performed a plurality of times as needed.

Regardless of direct substitution or indirect substitution, the liquid medium is replaced by setting the temperature of the liquid medium to preferably less than 100 ° C., more preferably 80 ° C. or lower, and further preferably 60 ° C. or lower. By setting such a temperature, evaporation of the liquid medium at the time of replacement is suppressed, and while maintaining a wet state and high dispersibility of copper particles, for bonding having excellent adhesion to other members. The composition can be obtained.

In the process of finally replacing the first liquid medium with the second liquid medium, the components derived from the first liquid medium that can cause impurities are efficiently removed, and the second liquid contained in the target bonding composition. From the viewpoint of improving the workability of replacement with a medium, the first liquid medium contained in the copper particle dispersion obtained by the wet reduction method is excluded from other liquid media (however, the first liquid medium and the second liquid medium are excluded. ) Is replaced at least once, and a second liquid medium is preferably used for the final replacement. That is, it is preferable to adopt indirect substitution as the present production method.

Further, when the first liquid medium is replaced with another liquid medium (however, the second liquid medium is excluded) multiple times, similarly, the first liquid medium is replaced with the first other liquid medium, and other liquid mediums are replaced. In each step of replacement between other liquid media when two or more liquid media are used, and replacement from the last other liquid medium to the second liquid medium, the dispersion is replaced while maintaining a wet state. Is preferable.
When the first liquid medium is replaced with another liquid medium more than once, the solid content concentration in each replacement step may be the same or different.
By replacing the liquid medium while maintaining the wet state of the copper particles, it is possible to obtain copper particles having high redispersibility and little deterioration while efficiently removing components derived from the first liquid medium that can cause impurities. Therefore, when the bonding composition containing the copper particles is sintered, the adhesion to other members can be further improved.

As one embodiment of the method of substituting the first liquid medium with another liquid medium one or more times, for example, the first liquid medium dispersion of copper particles obtained by the wet reduction method is used as another liquid medium such as water. There is a method of cleaning treatment using.
When the cleaning treatment is performed, for example, repulp cleaning, decantation method, rotary filter method, filtration and the like can be adopted as the method. When the cleaning treatment is performed, it is preferable that the copper particles after cleaning are subjected to the subsequent steps in the state of a dispersion that maintains a wet state.

When the copper particles are washed by the decantation method, for example, another liquid medium is added and the dispersion is washed until the conductivity is preferably 5 mS or less. The cleaning conditions at this time are, for example, when water is used as another liquid medium, the cleaning temperature is preferably less than 100 ° C, more preferably 15 ° C or more and 30 ° C or less. By carrying out under such conditions, it is possible to reduce impurities contained in the copper particles and to use the particles in the subsequent steps while keeping the particles uniformly dispersed. Then, the liquid medium dispersion of the washed copper particles is finally replaced with the second liquid medium while maintaining the wet state.

As another embodiment of the method of substituting the first liquid medium with another liquid medium one or more times, for example, the method described in Examples described later can be mentioned, but as long as the effect of the present invention is exhibited, the method is described. It can be applied without particular limitation on the number of replacements and the type of liquid medium used. Then, the liquid medium dispersion of the copper particles is finally replaced with the second liquid medium while maintaining the wet state.

Through the above steps, a bonding composition containing copper particles and a second liquid medium can be obtained. According to this production method, the dispersion treatment of copper particles when preparing a bonding composition is simplified, and the agglutination of copper particles is reduced, so that a highly smooth coating film can be efficiently formed. Become. Moreover, the deterioration of the surface of the copper particles can be reduced. As a result, when the coating film formed by the bonding composition is sintered, the meltability of the copper particles is increased, the meltability of the copper particles is increased, and the contact area between the melted particles and other members is increased. Can be increased. As a result, it is possible to obtain a sintered body that is less likely to crack or peel and has excellent adhesion to other members.

As the first liquid medium used in this production method, one or more of water, alcohol, ketone, ester and ether is preferable from the viewpoint of efficiently advancing the reduction of copper by the wet reduction method, and the copper particles by the wet reduction method are used. From the viewpoint of increasing the compatibility with the copper salt and increasing the production efficiency of copper particles, one or more of water and alcohol are more preferable.

Further, as the second liquid medium used in this production method, water, alcohol, ketone, ester, ether can be used as it is as a conductive paste or conductive ink from the viewpoint of increasing productivity. And one or more of hydrocarbons are preferable, and alcohol and hydrocarbons are more preferable.
The above-mentioned first liquid medium and second liquid medium may be the same as each other or may be different from each other.

When using another liquid medium (excluding the first liquid medium and the second liquid medium) from the viewpoint of achieving both a reduction in the residual amount of the first liquid medium and the ease of replacement with the second liquid medium, when using another liquid medium. As the other liquid medium, it is preferable to use one or more of water, alcohol, ketone, ester, ether and hydrocarbon, and it is more preferable to use one or more of water and alcohol.

Examples of the alcohol include monohydric alcohols such as methanol, ethanol, n-propanol, 2-propanol and n-butanol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, butylene glycol and pentylene. Polyhydric alcohols such as diols such as glycol and hexylene glycol, triols such as glycerin, and polyols such as polyethylene glycol and polypropylene glycol can be used.

Examples of the ester include the fatty acid ester of the polyhydric alcohol described above. The fatty acid is, for example, a monovalent fatty acid having a carbon atom number of preferably 1 or more and 8 or less, and more preferably 1 or more and 5 or less. The ester of the polyhydric alcohol preferably has at least one hydroxyl group.

As the ketone, a ketone having an alkyl group bonded to a carbonyl group having 1 or more and 6 or less carbon atoms, particularly 1 or more and 4 or less is preferable. Specific examples of the ketone include methyl ethyl ketone, acetone and the like.

Examples of the ether include chain ethers such as dimethyl ether, ethyl methyl ether and diethyl ether, and cyclic ethers such as octacene, tetrahydrofuran and tetrahydropyran.

Examples of hydrocarbons include aliphatic hydrocarbons such as hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, and hexadecane.

In the case of direct substitution, it is more preferable that the first liquid medium and the second liquid medium to be used are compatible with each other under the conditions of 1 atm and 25 ° C. Compatibility means a phenomenon in which two or more kinds of liquid components are mixed with each other to form a single phase in a fluid containing two or more kinds of liquid components.
By using a compatible liquid medium, it is possible to replace the first liquid medium with the second liquid medium while maintaining the dispersibility of the particles in the copper particle dispersion. In addition to this, it can be replaced with a second liquid medium in a state where the deterioration of the copper particles is reduced, so that when the obtained bonding composition is sintered, the meltability of the copper particles is increased and the copper particles are melted. The contact area between the particles and the surface of other members can be increased. As a result, it is possible to obtain a sintered body having high adhesion to other members and few impurities.

In the case of indirect replacement, when the first liquid medium is replaced with another liquid medium one or more times, or when the first liquid medium, the first other liquid medium, or another liquid medium is used for replacement twice or more. It is preferable that the other liquid media that are continuous in the process and the combination of the other liquid medium and the liquid medium of the second liquid medium at the end are compatible with each other, and at 1 atm and 25 ° C. It is more preferable that they are compatible with each other.
Further, in the case of indirect substitution, the first liquid medium and the second liquid medium may be compatible with each other under the conditions of 1 atm and 25 ° C., or may not be compatible with each other under the same conditions.
By using a liquid medium that is compatible with each other in the replacement of each liquid medium, it is possible to efficiently remove the components derived from the first liquid medium and other liquid media that may cause impurities. As a result, it is possible to obtain a sintered body having high adhesion to other members and few impurities.

Further, as one aspect of indirect substitution, the mixture was replaced with another liquid medium having a viscosity lower than that of the first liquid medium (however, excluding the first liquid medium and the second liquid medium) to reduce impurities in the dispersion. Later, it can be finally replaced with a second liquid medium having a higher viscosity than other liquid media (excluding the first liquid medium and the second liquid medium). The viscosity of the liquid medium can be measured by, for example, a vibration viscometer or a rotary viscometer.

Generation of copper particles by the wet reduction method described above, replacement of the first liquid medium with the second liquid medium, and, if necessary, replacement of the first liquid medium with another liquid medium, and from the other liquid medium. Each step of replacement with the second liquid medium is preferably carried out in the absence of the organic polymer, and more preferably carried out in the absence of the organic polymer throughout the entire steps of the production method of the present invention.
In this production method, in order to eliminate the organic polymer in the reaction system, for example, in each step of the reduction wet method and the replacement of the liquid medium, the organic polymer and the raw material containing the organic polymer are used. It's okay if it doesn't exist.
By performing each step in the absence of the organic polymer, the sintering of the copper particles is sufficiently advanced when the bonding composition is sintered while maintaining a low degree of aggregation of the copper particles. Can be made to. In addition to this, the content of residual organic matter, which is one of the impurities and can be a sintering inhibitor component, can be reduced, so that the density is high and the adhesion to other members is further excellent.

Examples of the above-mentioned organic polymer include natural polymers and synthetic polymers used as dispersants and surface treatment agents in the technical field. Details include, for example, proteins such as gelatin, and natural polymers such as gum arabic, casein, sodium caseinate, ammonium caseinate, starch, dextrin, agar, and sodium alginate. Synthetic polymers include cellulose compounds such as hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose and ethyl cellulose, polyvinyl compounds such as polyvinyl alcohol, and polyacrylic acid compounds such as sodium polyacrylate and ammonium polyacrylate. Can be mentioned.

The bonding composition obtained through the above steps is a dispersion containing copper particles and a second liquid medium. The bonding composition may contain only the second liquid medium as the liquid medium constituting the composition, or in addition to the second liquid medium, the liquid medium used for the liquid medium replacement up to that point. May be inevitably included. In any case, it is preferable that the second liquid medium is contained in the largest amount as a mass ratio among all the liquid media constituting the bonding composition.

The bonding composition is conductive as it is or, if necessary, by further adding at least one of metal particles other than copper particles contained in the bonding composition, a liquid medium, a binder resin, and the like. It can be used in the form of paste or conductive ink. That is, the present invention contains at least a bonding composition obtained through the above steps, and the composition and, if necessary, metal particles other than copper particles, a liquid medium, and a binder contained in the bonding composition. It also includes a method for producing a conductive paste in which at least one of the resins is further mixed.

Examples of the metal particles that can be further added to the bonding composition include particles containing metals such as copper, silver and gold.
The liquid medium that can be further added to the bonding composition is, for example, the same as that exemplified in the above description of the first liquid medium and the second liquid medium, and has good compatibility with the binder resin. Can be used.
Examples of the binder resin that can be further added to the bonding composition include one or more of acrylic resin, epoxy resin, polyester resin, polycarbonate resin, cellulose resin, and the like.

The bonding composition can be arranged between any two materials to be joined by a predetermined means or the like, and the two materials to be joined can be joined to form a joining structure. That is, the present invention also includes a method of arranging a bonding composition between two materials to be joined to join the materials to be joined and a method of manufacturing a bonding structure. As the material to be joined, a substrate, a semiconductor element, or the like can be used independently of each other. As a specific embodiment, for example, it can be used as a bonding agent for surface mounting an electronic device on a printed wiring board or as a material for filling vias in a printed wiring board. Further, it can be used for forming a wiring circuit of a printed wiring board or forming an electrode of a chip component.

Although the present invention has been described above based on the preferred embodiment, the present invention is not limited to the above embodiment. For example, in the copper particles obtained by the wet reduction method, as long as the effect of the present invention is exhibited, the obtained copper particles inevitably contain a trace amount of other elements, and the surface of the copper particles is inevitably a trace amount. It does not exclude being oxidized.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to such examples.

[Example 1]
In this example, a bonding composition was produced in the absence of an organic polymer in each step.
(1) Generation of Copper Particles by Wet Reduction Method In a 36 liter stainless steel tank, a mixed liquid medium of 5.0 liters of warm pure water and 5.0 liters of methanol as the first liquid medium and 2.5 kg of acetic acid as the copper source. Copper was added and stirred at a liquid temperature of 40 ° C. for 30 minutes to dissolve copper acetate. Next, 150 g of hydrazine was added all at once to the liquid medium, and then stirring was continued at a liquid temperature of 40 ° C. for 30 minutes to generate copper oxide particles in the liquid medium. After 30 minutes had passed, 1400 g of hydrazine was added to the liquid medium all at once, and then stirring was continued at a liquid temperature of 40 ° C. for 60 minutes to reduce the fine particles of cuprous oxide into fine particles of metallic copper. In this way, a dispersion in which the copper particles were dispersed in the first liquid medium was obtained. This dispersion remained moist. The particle size D _SEM50 of the obtained copper particles was 155 nm.

(2) Substitution of liquid medium In this example, the first liquid medium was replaced with another liquid medium a plurality of times, and then the second liquid medium was replaced as the final replacement. All steps were carried out while maintaining the wet state of the dispersion.
Specifically, as the first other liquid medium, pure water compatible with the first liquid medium was used. The first liquid medium dispersion of copper particles was washed with pure water until the conductivity became 3.5 mS by a decantation method to obtain a first dispersion in which copper particles were dispersed in water. The first dispersion remained moist.
Next, as the second other liquid medium, a modified alcohol (a mixed liquid medium of 89% by mass of ethanol and 11% by mass of 2-propanol) compatible with the first other liquid medium was used. The first dispersion was washed with a modified alcohol with a rotary filter until the water concentration in the first dispersion became 1% by mass or less to obtain a second dispersion in which copper particles were dispersed in the modified alcohol. This second dispersion remained moist.
Subsequently, as the second liquid medium used for the final substitution, hexylene glycol compatible with the second other liquid medium was used. After washing with hexylene glycol with a rotary filter until the modified alcohol concentration in the second dispersion becomes 3% by mass or less, hexylene glycol is solid-liquid separated by pressure filtration, and copper particles are used as the second liquid medium. A bonding composition dispersed in the above was obtained. This bonding composition maintained a wet state with a solid content concentration of 92%.

(3) Preparation of bonding paste 7.6 parts by mass of the bonding composition, 3 parts by mass of metal particles (copper particles, 1200YF, manufactured by Mitsui Metal Mining Co., Ltd.) other than copper particles contained in the bonding composition. 0.5 parts by mass of BIS-TRIS / hexylene glycol solution having a solid content concentration of 50% by mass and 0.1 parts by mass of polyethylene glycol 300 were mixed, and hexylene glycol was used as the balance to adjust the concentration of copper particles. A bonding paste containing copper particles was prepared so as to have a mass content of 76% by mass.

[Comparative Example 1]
Similar to Example 1, (1) after the copper particles were generated by the wet reduction method, the first liquid medium dispersion of the copper particles was washed with pure water by the decantation method until the conductivity became 3 mS. , Obtained a dispersion in which copper particles were dispersed in water. This dispersion remained moist.
Next, the dispersion was heated to 50 ° C., and while stirring, a dimethylglyoxime / methanol solution was added so that the dimethylglyoxime content was 0.5% by mass with respect to the copper particle content, and the liquid temperature was 50. The mixture was stirred at ° C. for 1 hour to obtain a water / methanol dispersion of surface-treated copper particles.
Then, the surface-treated copper particles were vacuum-dried to obtain dried copper particles. There is no liquid medium in these copper particles.
Finally, instead of the bonding composition, dried copper particles were used to prepare a bonding paste having the same composition and concentration as in Example 1.

[Evaluation of adhesion]
The bonding pastes of Examples and Comparative Examples are screen-printed on the center surface of a copper plate (length 20 mm x width 20 mm x thickness 2 mm) with dimensions of 10 mm in length × 10 mm in width × 110 μm in thickness, and the paste for bonding is printed at 110 ° C. It was dried for 20 minutes to obtain a dry film.
Next, an alumina plate (length 5 mm × width 5 mm × thickness 0.5 mm) whose surface is Ag-plated is placed on a dry film and baked at 6 MPa in a nitrogen atmosphere at a heating rate of 120 ° C./min at 280 ° C. for 20 minutes. The copper plate and the alumina plate were joined together.
After joining, use an ultrasonic flaw detector (manufactured by Hitachi Power Solutions, model number: FineSATIII) with a 75 MHz probe to observe from the surface side of the copper plate where the alumina plate is arranged by the reflection method, and sinter the dry film. The presence or absence of voids in the body and the state of the outer peripheral portion (non-pressurized region) of the alumina plate in the sintered body of the dried film were observed. The denser the sintered structure, the darker the color is observed. The results are shown in FIG.

In FIG. 1, the region where the alumina plate is arranged is indicated by reference numeral A, the region where the sintered body of the dried film exists is indicated by reference numeral B, and the region where the copper plate is exposed is indicated by reference numeral C.
As shown in FIG. 1A, in the sintered body of the paste obtained by using the bonding composition of Example 1, the region A in which the alumina plate is arranged is observed to be dark in color. It can be seen that a dense structure with few voids is formed and the bonding state between the alumina plate and the copper plate is good. Further, in the region B where the sintered body is located on the outer periphery of the alumina plate, the observed color was uniform, and peeling between the sintered body and the copper plate was not observed. Therefore, it can be seen that the paste using the bonding composition of Example 1 is excellent in adhesion to other members.

On the other hand, as shown in FIG. 1 (b), in the sintered body of the paste obtained by using the bonding composition of Comparative Example 1, the region A in which the alumina plate is arranged is observed to be dark in color. Therefore, it can be seen that the bonding state between the alumina plate and the copper plate is good, but in the region B where the sintered body is located on the outer periphery of the alumina plate, the observed color is non-uniform, and the sintered body and the sintered body are in a non-uniform state. Many peelings from the copper plate were observed. Therefore, it can be seen that the paste using the bonding composition of Comparative Example 1 is inferior in adhesion to other members.

According to the production method of the present invention, it is possible to obtain a bonding composition having excellent adhesion to other members at the time of sintering.

Claims

Copper particles are generated in the first liquid medium by a wet reduction method to prepare a dispersion of the copper particles, and then after that,
While maintaining the wet state of the dispersion, the first liquid medium of the dispersion is finally replaced with the second liquid medium to obtain a bonding composition containing the copper particles and the second liquid medium. A method for producing a bonding composition.
The production method according to claim 1, wherein the liquid medium is replaced at a temperature of less than 100 ° C.
The production method according to claim 1 or 2, wherein one or more of water, alcohol, ketone, ester, ether and hydrocarbon is used as the second liquid medium.
The production method according to any one of claims 1 to 3, wherein the copper particles have a volume cumulative particle size D SEM50 of 100 nm or more and 300 nm or less in a cumulative volume of 50% by volume measured by a scanning electron microscope.
The method for producing a composition according to any one of claims 1 to 4, wherein the first liquid medium is replaced with another liquid medium at least once, and the second liquid medium is used for the final replacement.
The production method according to claim 5, wherein the first liquid medium is replaced with another liquid medium while maintaining the wet state of the dispersion.
The production method according to any one of claims 1 to 6, which is carried out in the absence of an organic polymer.
A method for producing a conductive paste containing a bonding composition obtained by the production method according to any one of claims 1 to 7.
A method for joining a material to be joined, wherein the composition for joining obtained by the production method according to any one of claims 1 to 7 is arranged between two materials to be joined.